53be502822
The perf ftrace latency is to get a histogram of function execution
time. Users should give a function name using -T option.
This is implemented using function_graph tracer with the given
function only. And it parses the output to extract the time.
$ sudo perf ftrace latency -a -T mutex_lock sleep 1
# DURATION | COUNT | GRAPH |
0 - 1 us | 4596 | ######################## |
1 - 2 us | 1680 | ######### |
2 - 4 us | 1106 | ##### |
4 - 8 us | 546 | ## |
8 - 16 us | 562 | ### |
16 - 32 us | 1 | |
32 - 64 us | 0 | |
64 - 128 us | 0 | |
128 - 256 us | 0 | |
256 - 512 us | 0 | |
512 - 1024 us | 0 | |
1 - 2 ms | 0 | |
2 - 4 ms | 0 | |
4 - 8 ms | 0 | |
8 - 16 ms | 0 | |
16 - 32 ms | 0 | |
32 - 64 ms | 0 | |
64 - 128 ms | 0 | |
128 - 256 ms | 0 | |
256 - 512 ms | 0 | |
512 - 1024 ms | 0 | |
1 - ... s | 0 | |
Committer testing:
Latency for the __handle_mm_fault kernel function, system wide for 1
second, see how one can go from the usual 'perf ftrace' output, now the
same as for the 'perf ftrace trace' subcommand, to the new 'perf ftrace
latency' subcommand:
# perf ftrace -T __handle_mm_fault -a sleep 1 | wc -l
709
# perf ftrace -T __handle_mm_fault -a sleep 1 | wc -l
510
# perf ftrace -T __handle_mm_fault -a sleep 1 | head -20
# tracer: function
#
# entries-in-buffer/entries-written: 0/0 #P:32
#
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
perf-exec-1685104 [007] 90638.894613: __handle_mm_fault <-handle_mm_fault
perf-exec-1685104 [007] 90638.894620: __handle_mm_fault <-handle_mm_fault
perf-exec-1685104 [007] 90638.894622: __handle_mm_fault <-handle_mm_fault
perf-exec-1685104 [007] 90638.894635: __handle_mm_fault <-handle_mm_fault
perf-exec-1685104 [007] 90638.894688: __handle_mm_fault <-handle_mm_fault
perf-exec-1685104 [007] 90638.894702: __handle_mm_fault <-handle_mm_fault
perf-exec-1685104 [007] 90638.894714: __handle_mm_fault <-handle_mm_fault
perf-exec-1685104 [007] 90638.894728: __handle_mm_fault <-handle_mm_fault
perf-exec-1685104 [007] 90638.894740: __handle_mm_fault <-handle_mm_fault
perf-exec-1685104 [007] 90638.894751: __handle_mm_fault <-handle_mm_fault
sleep-1685104 [007] 90638.894962: __handle_mm_fault <-handle_mm_fault
sleep-1685104 [007] 90638.894977: __handle_mm_fault <-handle_mm_fault
sleep-1685104 [007] 90638.894983: __handle_mm_fault <-handle_mm_fault
sleep-1685104 [007] 90638.894995: __handle_mm_fault <-handle_mm_fault
# perf ftrace latency -T __handle_mm_fault -a sleep 1
# DURATION | COUNT | GRAPH |
0 - 1 us | 125 | ###### |
1 - 2 us | 249 | ############# |
2 - 4 us | 455 | ######################## |
4 - 8 us | 37 | # |
8 - 16 us | 0 | |
16 - 32 us | 0 | |
32 - 64 us | 0 | |
64 - 128 us | 0 | |
128 - 256 us | 0 | |
256 - 512 us | 0 | |
512 - 1024 us | 0 | |
1 - 2 ms | 0 | |
2 - 4 ms | 0 | |
4 - 8 ms | 0 | |
8 - 16 ms | 0 | |
16 - 32 ms | 0 | |
32 - 64 ms | 0 | |
64 - 128 ms | 0 | |
128 - 256 ms | 0 | |
256 - 512 ms | 0 | |
512 - 1024 ms | 0 | |
1 - ... s | 0 | |
#
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Changbin Du <changbin.du@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20211215185154.360314-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.